Railroad tracks are typically supported by cross ties, typically made of wood, that run the width of the tracks, and are attached thereto by spikes. The cross ties rest upon ballast, which typically consists of gravel, crushed rocks or the like. The ballast typically shifts over time, with movement. Ballast tamping tools, which are machines that run along the railroad tracks, are used to tamp the ballast back into place around the cross ties so that the cross ties and the tracks attached thereto are adequately supported.
Ballast tamping tools have a reciprocating tamping drive, that move and vibrate shafts attached to the drive such that a pair of spaced-apart shafts, and the ballast blades, or paddles, attached to the other end of the shafts move towards and away from each other, tamping and compressing the ballast positioned under and around the cross ties. The ballast blades undergo a great deal of wear as a result of repeated contact with the ballast and edges of the cross ties, especially the face of the blade that is pressed against the ballast. When the blades wear out, chip, or snap off, they no longer perform the tamping task effectively, and must be replaced. To replace the shafts and/or attached blades necessitates shutting down the entire machine and removing the shaft(s) with worn or damaged blades. The necessity to shut down the equipment is obviously time-consuming, and reduces productive operating time for the equipment.
Therefore, what is needed is a system and method for enhancing the life of the blade to extend the interval at which blades must be replaced or repaired. A variety of devices and enhancements have been developed to help prolong the life of the ballast tamping tool shaft blade, or to simplify replacement of the blade.
For example, U.S. Pat. Nos. 3,581,664, 4,062,291 and 4,068,594 disclose tools in which the blade is secured to the end of the shaft with one or more screws so the blade can be easily removed when it has worn and needs to be repaired. However, in use, it was found that the vibrating motion of the tamping machine tended to loosen, or back out the screws such that the blades would detach from the shafts.
U.S. Pat. No. 4,160,419 discloses a system where the blade is rectangular and is gradually tapered from one side to the other so that the blade can sustain a greater amount of wear. However, this mechanism is complex, and must be opposed with a blade that is tapered in the opposite direction, necessitating more work and keeping multiple parts in stock.
U.S. Pat. No. 4,501,200 discloses a system that attaches the tamping blades to the shaft in a method that simplifies replacement of the blades, combined with blades having a hardened working face. However, this system requires replacement of the standard shaft with the special system of the patent.
U.S. Pat. No. 5,261,763 discloses a tool in which bits of hardened material have been attached to the blade. However, the hardened material is configured such that it has a ledge at the lower end which underlies the lower end of the blade. The configuration is such that the ledge of the hardened material is prone to catching on the ballast, detaching the hardened material from the underlying blade during use.
Thus, an on-going need exists for a tamping tool mechanism in which the necessity to replace the shaft blade is reduced or simplified.